Furnace for treating metal



wAug. 7, -192.8. v l l67 w. E. wATKlNs 9'389 FURNACE Foa TREATING METAL Y origin-.a1 Fileg aan. 6, 1927 Figa..

INVENTOR. v

www 5. Mat/nhs ATTORNEYS Patented Aug. 7, 1928.

UNITED STATES PATENT OFFICE.

WILLIAM-E. WATKINS, OF NEW YORK, N. Y., ASSIGNOR TO COPPER PLATE SHEET AND TUBE COMPANY, 0F NEW YORK, N. Y., A CORPORATION OF NEW JERSEY.

FURNACE FOR TREATING METAL.

Original application led January 6, 1927, Serial No. 159,337. Divided and this application lei June 25, 192,7. Serial No. 201,317.

This invention relates to methods of plating one metal with another and apparatus therefor; and more particularly to a process of forming a film of a plating metal on the metal to be plated in which the plated metal is coated with a plating suspension of the plating metal in finely divided condition, or a reducible compound thereof, and passed through a furnace to heat the metal and the plating suspension to form an adherent layer` of the plating metal on the metal to be plated.

In a prior4 Patent, No. 1,197,693, granted Sept. 12th, 1916, I have described and claimed a process of plating metal in which a metal plating suspension, such as a mixture of an oxide of the plating metal and an oil, is applied to the metal to be plated and the metal heated to reduce the oxide and form a continuous film of the plating metal on the metal to be lated. To insure the reduction of the oxide to metallic form, finely divided carbon, or. other reducing agent, may be added to the metal plating suspension as disclosed and claimed in my prior Patent, No. 1,197,694, granted Sept. 12th, 1916. The lating metal in finely divided form may he substituted for the reducible compound and mixed with a suitable vehicle such as a semi-liquid or viscous hydrocarbon and applied to the metal to be plated by coating the base with the plating suspension and heating as described in my prior Patent, No. 1,197,695, granted Sept. 12th, 1916.

In plating metals according to the proeesses disclosed in in prior patents, the metal to be coated an the suspension thereon is heated to a temperature above the melting point of the plating metal. Thus, When ferrous metals are coated with copper, thev metal is heated to a temperature approximating the melting temperature of copper, or to a temperature of substantially 2000O F.

I have found that a superior plated product may be obtained if the metal is heated merely to the sintering temperature of the plating metal. Within their4 sintering temperature range, metals possess sufficient freedom of movement to 4enable them to coalesce. I have discovered that by heating the metal to be plated with the metal plating suspension thereon to the sinterng temperature of the plating metal, it

is possible to produce films of uniformly beautiful appearance and possessing a degree of continuity not possible when the film has been allowed to reach itsmelting temperature. als, I propose to heat the metal with the coating applied thereto to a temperature of about 1800O F. which is sufiicient to permit the copper to coalesce and form a continuous coating. I have further foundthat the best results are obtained if the film of plating metal is kept below its sintering temperature until the metal base has reached the proper temperature. I accordingly preheat the base on. which the coating film has been applied to a` temperature just below the sintering temperature of the plating metal and then raise the temperature to the sintering temperature of the plating metal to form the adherent film or layer on the base.

A further object of the invention is to provide a furnace having a preheating zone in which the metal base may be properly preheated before the plating film reaches its sintering temperature. I accordingly provide a furnace having a preheating zone, a heat treating zone, a cooling chamber and a combustion chamber and regulate the passage of the products of combustion through the furnace in such manner that the metal on which the coating has been applied is first preheated, then raised to the sintering temperature of the plating metal and then cooled before reaching the air to such a temperature that it Will not readily oxidize When exposed to air.

In the following illustration of the invention I have described the application of copper plating to ferrous strips. The invention may be applied to the coating or plating of other metals and other plating metals may also be employed. It Will be apparent that the process is equally applicable to the coating of plates or sheets as Well as strips.

In the accompanying drawings- I have diagrammatically illustrated a type ofy furnace particularly useful in practicing the process and forming a part of theinvention. In this showing, Fig. 1 is a vertical, longitudinal, sectional view of the furnace;

Fig. 2 is a vertical, transverse, sectional viev, substantially on line 2-2 of Fig. 1; an

Thus, in coating ferrous met- Fig. 3 is a similar view on line 3-3 of Fig. l.

The furnace 1s preferably rectangular and consists of outer Walls, 1, a floor, 2, and a roof, 3, preferably lined with silocel or similar material. Vithin the furnace I provide side walls` 4, a fioor, 5, and an inner roof, 6, of tire brick. The interior of the furnace is in the form of a` large open chamber, the lower portion of the front of which is the combustion chamber 9 provided with a roof 7 above which at a suitable height is the roof of the furnace. The preheating chamberl or zone is formed by the space between the roof of the combustion chamber and the roof of the furnace. The length of the preheating zone is fixed by the length of the combustion chamber roof. A burner block, 10, is arranged intermediate the ends of the combustion chamber and an oil burner, 11, projects through an opening in this block. The oil` burner may be supplied with the proper mixture of air and fuel in any Suitable manner. The portion of the furnace in the rear of the preheating Zone and combustion chamber forms a heat treating zone, 12. A foot arch, 13, is Aarranged at the back of the artition, 7, and curves downwardly to the oor of the furnace so that the products of combustion from the combustion chamber, 9. are forced to travel around this arch in enteringr the heat treating zone. The hot gases issuing from the combustion chamber are thus divided equally by the foot arch. At the rear of the furnace, I provide an opening, and a cooling chamber, 14, is connected to the furnace at this opening. The cooling chamber is of such length that the strips in passing through it will be cooled to such tempera-ture that they may then be passed into the open air Without danger of oxidation. Suitable rollers, 15, may be arranged at the end of the cooling chamber. A ramp, 16, may be builtin the back of the furnace to prevent the gases from pocketing therein. Suitable means are provided for controlling the temperature in the various portions of the furnace. A stack, 17, is arranged adjacent the rear of the furnace and communicates with the interior through an opening, 18. The size of this opening may be a justed by means of slidable dampers`19. A similar stack, 20, is arranged at the rear of the cooling chamber and the flow of gases through this stack is controlled by a damper, 21. A stack, 22, is arranged adjacent the front of the furnace and provided with a. damper, 23. A baffle, 24, may be arranged depending from the roof of the furnace and separating the preheating zone from the heat treating zone. The strip of metal to be treated ispassed through' the furnace in catenary form a indicated at A and as' described and claimed in my copending application, Serial No. 144,685, led Oct. 28th,

1926. The strip is supported by the rollers, 15, in the cooling chamber and by a suitable guide, 25, arranged at the front of the furnace.

In practicing the process the strip is` first coated on one or both sides with a suspension of a reducible compound of the plating metal or the metal in finely divided form and a liquid spreading medium of a reducing character which serves to protect both the plating metal and the metal lo be plated during the plating operation. An asphaltic base hydrocarbon oil having a viscosity of 110 has been found satisfactory as possessing the proper spreading and binding qualities while its base contains sufficient carbon to reduce any oxides that may be present. vWhen 5 grammes or less of the plating metal is to be applied to each square foot of,

surface, the finely divided metal and oil are mixed in the proportion of 40 percent finely divided metal and 60 percent oil. For films of greater thickness a mixture richer in *finely divided metal has been found satisfactory. The metal strip is passed through the furnace and the products of combustion from the burner, 1l, pass from the combustion chamber around the foot arch, 13, into the heat treating chamber, 12. The temperature to be maintained in the heat treating chamber will depend upon the speed of travel of the metal being treated. In a furnace of this type, approximately 25 feet long, the heat treating zone may be maintained at a. temperature of 2250O F. to treat a strip 12" X .05 when the strip is traveling at a speed of 80 feet per minute. Under these" conditions the strip Will be heated to a temperature of substantially 1800o F., in passing through the heat treating zone. A pyroinetcr, 2G, may be placed in the heat treating zone by passing it through the wall or roof of the furnace. The preheating zone may also be provided with a pyrometer, 27, and the temperature in the preheating zone should be maintained under that of the heat treating zone to prevent the plating metal from reaching its sinterin temperature before the metal base is at t e right temperature to receive it. The furnace gases should be slightly reducing and maintained at a pressure sufficient to prevent leakage ,of atmospheric air in the furnace. The pressure within the furnace causes the gases to travel in both directions when they enter the heat treating zone thereby causing a portion of the gases to pass through the preheating zone to the stack, 22. The baiiie, 24, retards the How of gases into the preheating zone and thus assists in maintaining a lower temperature in this zone than in the heat treating zone. The temperature of the preheating zone may also be regulated by the damper, 23. The main control of the How of gases toward the preheating zone and the cooling chamber, 14, is accomplished by means of the sliding blocks or dampers, 19, over the opening, 18, and by properly regulating the size of the opening, 18, the temf perature in the various zones may be positively controlled.

The furnace may be operated at constant temperatures in the several zones and the speed of travel of the metal through the furnace may be regulated to suit the gauge of the metal being treated. The process can, of course, be modified to treat different metals and in each instance, the temperature of the heat treating zone andthe speed of travel of the strip is regulated to heat the metal to the sintering temperature of the plating metal. To produce a bronze plating, the plating suspension is .formed of a mixture of cupric oxide and tin oxide (or, preferably, finely divided copper, and tin oxide) in definite proportions to produce the desired bronze, to Which the proper quantity of the spreading vehicle or oil is added.

This application is a division of my copending application filed Jan. (5th, 1927, Serial No. 159,337, the claims of the said application being drawn to the process herein disclosed, and the claims of this application being drawn to the apparatus.

I claim:

1. A furnace consisting essentially of a chamber having a horizontal dividing Wall the front portion of the furnace into a combustion chamber and a preheating zone, the portion of the chamber in the rear of said horizontal dividing wall forming a main heating zone, and a damper to control the flow of products of combustion through the preheating zone and the main heating zone. 3. A furnace'consisting essentially of a chamber having a horizontal dividing Wall arranged in the front end thereof to divide the front portion of the furnace into a combustion chamber and a preheating zone, the portion of the chamber in the rear of said horizontal dividing Wall forming a main heating zone, a damper to control the flow of products of combustion through the preheating zone and the main heating zone, and a baffle Wall between said preheating zone and the main heating zone. l

In testimony whereof I ailix my signa,- ture.

WILLIAM E. WATKINS-` 

